FDA Study Shows Raw Pet Diets Contaminated with Potentially Deadly Bacteria Much More Frequently than Cooked Pet Foods

Numerous studies have demonstrated that raw diets are likely to be contaminated with potentially harmful bacteria, including Salmonella, E. coli, and others that can cause serious disease. (1, 2) Though cases of illness have been documented caused by these organisms in raw foods, it is not clear how great the risk is for pets or for humans handing raw pet food or living with pets eating such diets. And it is true that cooked commercial diets have been found to be contaminated with such bacteria as well, which advocates of raw foods have sometimes used as evidence that raw diets are no riskier than cooked. A new FDA study, however, shows quite clearly that the risk of bacterial contamination is far greater for raw pet diets than for cooked commercial foods.

The Pet Food Study was a two-year survey of pet foods that evaluated over 1000 samples. Raw foods were only included in the second year of the study, in which 196 samples of commercial raw diets were tested.  The table below compares the occurrence of two important pathogenic bacteria in dry cooked diets and raw diets.

fda pet food study table


Clearly, both bacteria are far more likely to be found in uncooked than in cooked pet foods. The prevalence of Listeria was particularly alarming because 90% of people infected with this bacterium are hospitalized, and 20-30% die. While the annual number of cases of this disease is small, it makes no sense to risk a serious and frequently deadly illness in order to provide a raw diet for your pet which has not been shown to have any health benefits for them.


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31 Responses to FDA Study Shows Raw Pet Diets Contaminated with Potentially Deadly Bacteria Much More Frequently than Cooked Pet Foods

  1. Pingback: Raw Diets for Pets | The SkeptVet Blog

  2. Frances says:

    While I would consider myself an agnostic when it comes to raw feeding (my animals get a variety of raw and home cooked foods), I don’t find this research surprising, or a reason not to feed raw. Surely everyone knows raw meat can contain pathogenic bacteria – it is why I was taught at my mother’s knee to take sensible precautions when preparing it for human or canine consumption. The reason that I find reports of salmonella contamination in kibble and other processed foods more concerning is that few people would consider it necessary to take the same precautions for what is considered a “safe” packaged food. The risk would seem to be greater for the humans handling the food than the animals eating it; dogs with a healthy immune system can ingest foods that would make a human violently ill – they have survived as scavengers for millennia.

  3. skeptvet says:

    While appropriate handling precautions can reduce the risk for humans, again the big question is why take any risk of a deadly disease if there is no benefit? Until the benefits of raw diets are demonstrated by something more than anecdotes, it doesn’t makes sense to do so.

    As for the susceptibility of dogs to pathogenic bacteria, the common claim that they are not susceptible or much more resistant than humans hasn’t been demonstrated either. They have been “scavengers” of our table food for millennia, which has meant mostly cooked food, for one thing. And for another, dogs scavenging garbage dumps are far less healthy and liver shorter lives than well cared for pets, so it also doesn’t make sense to suggest we shouldn’t be worried about the potential health risk to our pets from bacterial contamination of raw meat simply because dogs who are not well cared for have had to live with this risk.

  4. Beccy Higman says:

    Surely the contamination risk depends on the source of the raw food? I feed raw which I get from my local butcher, they still break down whole carcasses rather than buying in pre-cut portions. This means the meat is human quality, but is the things from the carcasses that don’t sell so well along with things like chicken frames. They put it away in the freezer for me daily and I pick it up once a week. Have to say the dogs don’t always get it all if I want to make stock!

    I started doing this after my first GSD seemed to respnd to the bought foods by being hyperactive, a change to raw stopped the continual pacing within a week. Anecdotal of course, and a better quality prepared food might also have sloved the problem.

  5. v.t. says:

    Beccy, you don’t think butcher shops are immune from contaminants?

  6. skeptvet says:

    The contamination comes from bacteria in the animals being slaughtered, primarily in their GI tracts. These organisms commonly contaminate the parts of the animals we eat, which is humans almost always cook our meat before eating it. Though slaughter practices can increase or reduce the risk of such contamination, there is no such thing as a perfect process, so regardless of where your meat comes from, it will sometimes be contaminated with pathogens. As you know, outbreaks of foodborne illnesses like these occur in humans regularly, though they are far fewer in extent and frequency than they might be due to food handling regulations and appropriate cooking and sanitary practices in the home.

    All of this is just to say that there is still some risk wherever you get your meat. And, of course, the issue of whether that risk is worth it depends on what benefits there are to feeding raw. While I understand the impact of anecdotal observations, they have proven unreliable. There is no plausible mechanisms by which the diet change you describe could have the effects you perceived in your pet, and there is no objective real-world evidence that it would, other than these sorts of anecdotes. And if you collect enough anecdotes like this, raw food apparently has every possible effect, from making animals calmer to more energetic, stools softer or firmer, and so on. I still think, unfortunately, that it’s a situation of benefits unknown, if any, and risks know though probably small. It’s no consolation if someone’s infant or grandparent dies of Listeriosis to know that it doesn’t happen often.

  7. Frances says:

    As you say it comes down to risk assessment. I have decided that I am happier sourcing ingredients and managing my animals’ diet myself, including giving them raw tripe and carefully selected raw bones to chew, than feeding mass produced, processed food and treats which carry risks that I do not control. That decision might well change if anyone in the household were immuno-compromised, or otherwise at risk. It would be very interesting to get solid, research-based data on the comparative incidence of severe gastro intestinal disease and of allergy issues in dogs fed on the various diets, though – at present there seems to be research into what goes in, and what comes out, but very little into the effect of the food on the dogs themselves!

  8. Beccy Higman says:

    I realise that and again it comes down to the quality of the source, good slaughter and gutting technique make a lot of difference to the level of faecal contamination. My household doesn’t have any at risk humans, I take the appropriate precautions when handling all meat and it has been frozen which does reduce the viability of most bacteria.

    I have wondered whether the behavioural difference was down to the amount of energy in the food, I might well have had the same result from reducing the amount fed. The other problem could have been food colouring, though I’ve yet to see a definitive study on the behavioural effects of those in humans, let alone dogs. Ultimately I don’t know that it was the change in food that made the difference for that dog, but my dogs thrive on the diet and because of the source it is actually significantly cheaper than any of the alternatives. I haven’t seen anything that convinces me my present dogs would do better on a commercial food. If I rescued a dog with say tooth problems I’d have no problem feeding them a good commercial food.

  9. Diane says:

    I, too, am concerned about the ingredients/contaminants that may be in my pets’ commercial food, but that’s a separate issue from whether the ingredients/contaminants are cooked or not. What do you consider the benefits of not cooking your pet’s food? Or is it just a general concept that dogs should have the same diet as wolves, and wolves eat their kill raw?

  10. Diane says:

    Regarding bones & broken teeth–In a previous job I dealt with the veterinary concerns of a population of about 3,000 dogs (mostly Labs) for 5 years. Fractured teeth were a fairly common complaint and although the cause wasn’t always known, when it was known, the cause was chewing on one of 3 things, in descending order of frequency: Nylabones, real bones, and rocks.

    My impression is that people who like to give their dogs bones seem to consider broken teeth an unlikely and minor risk that they’re willing to take. But I suspect they would reconsider if they realized how common tooth fractures really are and how they often result in pulp exposure, how painful that is and how it offers entry into the bloodstream for unfriendly microorganisms (an especially unpleasant prospect if you’re feeding a raw diet), how the tooth may become abscessed, and how severe an abscessed tooth can get. And how l o n g their dog could be suffering from a broken tooth before they discover it. And that such fractures will require their dog to undergo anesthesia–something both scientists and holistic-etc. people can agree is a bad thing to undergo if you can avoid it (and it’s easy to avoid deliberately giving your dog objects that can break his teeth). And how expensive it can be to have a tooth extracted. Particularly since the most common teeth broken in this way seem to be carnassials, and how difficult/traumatic/expensive carnassials are to extract, and how a good number of vets prefer to refer out carnassial extractions to a boarded dentist, resulting in even higher cost. Or if they prefer a root canal, that is even more expensive. And how their dog may break more than one tooth. Etc. etc. etc.

    I think if people were really aware of these things they would not give their dogs bones to chew on. As for the possible benefit of reducing tartar/dental disease, it’s a lot safer to brush your dog’s teeth or give them dental chews.

  11. v.t. says:

    Great post, Diane!

    Let’s also add regular checkups – oftentimes those dental problems are found early (provided the client gets the dog in regularly) and result in less procedures and costs.

  12. Beccy Higman says:

    I don’t have tooth fracture problems because they don’t get the heavier bones, just things like ribs.

    These days I feed raw mainly because they like it better, especially the oats which they don’t like at all cooked, which is fine by me as it saves an extra step. It also means I can give them the bones which have less tendency to splinter when raw.

  13. skeptvet says:

    Good point, Diane. We have a full-time dentistry service Mon-Fri that treats 4-6 animals a day, and we see a LOT of fractured teeth. Bones and rocks are the most common causes. Definitely a real risk.

  14. Diane says:

    Isn’t it odd how many dogs will chew on rocks?! Labs I understand because they’ll eat anything, but do you see a lot of breeds doing that?

    v.t.–So true about wellness visits, and for a lot more than just dental issues.

    Beccy, I guess it depends on the size of your dog’s mouth and the size of the ribs. But it’s an interesting point about whether bones splinter or not when they’re raw. I’ve also heard that they don’t, but I’m not sure where the idea comes from or whether any research has been done on it. Just based on the fact that living bones can break very sharply from trauma, it seems likely to me that raw bones could also break sharply. Maybe skeptvet has more info on this subject.

  15. Art says:

    I heard a boarded vet nutritionist lecture Thursday about raw pet diets. the lecture was paid for by a local bank not a pet food company. He thought any improvement from eating a raw diet was due to the increase in fat content from the additional meat in the raw diet. He claimed he was able to produce similar results just by increasing the fat content of the dry dog food.

  16. Diane says:

    Art, that is very interesting; did he say what kind of improvements were noticed?

  17. Art Malernee Dvm says:

    He did not say. I was going to ask him if results were temporary but never got around to it. I remember studies thirty years ago when we sold a lot of fatty acid supplements supposably for glossy coats in dogs or told the client to add corn oil and bacon dripping to the dog food that the studies showed the positive effects on the skin only lasted about a month. So the people selling the supplements could show a benefit just not one that lasted if the dog continued taking the supplement. I had copies of that study years ago I will see if I can find it.

  18. fluidtherapy says:


    Without in any way being confrontational, I might oh-so-carefully disagree that undergoing anesthesia is a “bad” thing. I know the alties and naturalists default to such a conclusion — without a shred of definitive evidence — because it is what it is: manipulation of the natural status with chemicals. But, I’ve yet to see a study that documents the deleterious effects of recognized anesthetic protocols in/on an otherwise healthy body as “bad”. Are there risks? Yes, but we all (presumably) take the necessary acts to preclude or lesson said risks. And, of course, the benefits of the actions requiring anesthesia must outweigh those risks.

    So, while I understand the point that if one doesn’t have to undergo anesthesia then one shouldn’t. I would also point out the fact that we (as a profession/society) do a lot of things on a more or less routine/regular basis that involves anesthesia; and I don’t see information or reports that describe such as necessarily “bad”.

    Just wanted to make that point.

  19. Diane says:

    Hi fluidtherapy, it sounds like I didn’t articulate that bit about anesthesia as well as I meant to.

    I didn’t mean to suggest that anesthesia is bad, just that anesthesia for no good reason is bad, in the same way that any unnecessary medical procedure is bad (IMO, and I believe just about everyone would agree), but especially one with known risks, and most especially when those risks are potentially very serious. Because yes, you can do lots of things to mitigate the risks of anesthesia, but you can’t completely eliminate them, and they are indeed very serious. Hence anesthesia release forms.

    But I’m not picking on anesthesia. Or bones, for that matter. I’m against unnecessary risks overall. Failing to get important vaccinations, failing to use tick control or heartworm control, letting your dog run around the neighborhood loose, letting a puppy destroy and eat things like rope toys, taking off a post-sx e-collar because your dog looked SO sad, waiting to see if your dog gets sick after eating something obviously toxic–these are also risks I consider just silly. I kid you not that I was once on the phone with a client whose dog was undergoing his second sock FB obstruction surgery in 6 months, when the client says to me, that’s the 12th sock the dog has eaten that he knows about so far this year (and it was August!). I wanted to say, Why in hell don’t you pick up your @#$% socks???

    Sorry for the rant…This sort of stuff was the constant bane of my existence in my last job…And apparently it’s still under my skin. 🙂

  20. fluidtherapy says:

    Diane, thanks for the reply. I understand your position, precisely.

  21. Beccy Higman says:

    Sorry not to reply sooner Diane, we’ve all been on holiday.

    I have GSD’s so to them ribs and the like are quite small bones. I don’t know what changes cooking produces in bone, but my perception is that they are more brittle. Certainly I know friends who give their dogs the stuffed cooked bones have to keep a very close eye on them as they do splinter, but they are, I think, leg bones. I think it may be as much about which kind of bone as about whether it’s is raw or cooked, the raw sites always advise against ‘weight bearing’ bones. It’s not that so much that raw bones can not break, but that the smaller ones like ribs have a degree of ‘give’ when they are raw that they don’t seem to have when cooked. Rib bones are quite soft, you can cut them off the spine with secataurs. I am not explaining this well and I don’t have anything but anecdotal evidence.

    Art that is an interesting suggestion about the comparative fat levels and certainly makes sense.

  22. kaimeju says:

    I have a question about this study, actually. This was conducted during the massive Diamond Pet Food recall and yet no samples of dry dog food turned up contaminated. Is this because they excluded these products, or just product from that specific manufacturing facility, or what? Why did they do this? Also there were no recalls of commercially-prepared raw foods during the second year of the study. “In the second year spanning from October 2011 through July 2012.” If 7% of their samples were showing up contaminated, why were those companies not executing recalls? I saw there were several recalls of raw foods from 2012-2013, AFTER the study was completed. Were they just late to the party…or what? Also, commercially prepared raw foods account for less than 1% of the total pet food market. Why did the study have 196 samples of raw food and only 120 of dry kibble? Without a doubt, you’re going to have more samples per manufacturer of the raw diets. There are well over 400 varieties of commercial dried kibble but only about 30 types of raw diets. How can you possibly compare the two based on this study?

    If you look at what recalls have actually occurred over the past three years, it becomes apparent that nobody is immune- not raw food, not dry food, not semi-moist or even pig ears. The numbers released by the FDA make it appear to consumers that dry kibble is completely salmonella-free, which is not the case. I think this is irresponsible reporting of data.

  23. skeptvet says:

    Any sample is going to be only a snapshot of the situation at the moment, and will reflect the population sampled. The point is not that dry diets do not experience salmonella contamination, because they do. The point is that raw diets in this study showed much higher rates of such contamination. If this is a fluke of the sampling, then replication of the study should produce different numbers. While there are good reasons to believe raw diets are more prone to contamination with infectious organisms (which is, after all, the main reason humans eat almost exclusively cooked meat), it is true individual studies are never defintive, This is the best data on the question we have so far, but it is only one study. Time will tell if the results of future surveys are consistent with this one.

  24. if this study isn’t done by the pet food industry I would be surprised! Raw food diet is fine as long as you are using good meat to start with… in the right combination, of some heart and / or liver / a raw egg or a sardine or two…with some of the necessary supplements – it really the best food…. the second would be the same with the frozen meat version.
    I think a lot of humans are eating foul meat or bad meat without realizing it… I sure they would find a similiar study…

    The best quality product is the best food…. a cat only eats 100grs a day so it REALLY doesn’t break the budget – a big dog is another menu….but doable when you only have 1…

  25. skeptvet says:

    1. The study was done by the FDA, so your implication that it was industry funded, or that such funding would justify ignoring the results, is just a bit of vacuous conspiracy theorizing on your part. It is a cheap way for you to ignore evidence that conflicts with what you want to believe.

    2. You assert raw is “the best food,” but once again you persist in the belief that your belief itself matters. If you have evidence, you are free to present it. If all you have to say is “You’re wrong because I believe something else,” then there really is no reason for people to take you seriously. You have no special insights, and your belief is no more evidence for what you claim than mine or anyone else’s. Evidence is what matters, not personal belief.

  26. Anne-Louise Koehl says:

    The reason we are of different opinions as we come from different countries with very different legislation and control when it comes to agriculture produce and animal produce. I work very closely with 3 vets and here we promote a raw meat diet with taurine and necessary additions to complete the needs of the cat in this instance ! We have no experience as yet of animals having a “ailment” as a result of eating such a diet.

    The big controversy is the condition of the animals USED in our food chain. There have been numerous scandals on this subject lately in the news in the USA and other countries and with this in mind I can understand the BIG GUNS of your counter!

    If a cat could choose he would eat mice ! He doesn’t need FDA approval! And I ask is the FDA always operating with integrity ? These are all important angles to look at when analyzing “scientific information” which I respect…but also check the how’s, when’s and why’s and especially the who’s doing testing and research and under whose funding! The other question to look at is the pet food industry, whose integrity is not always dictated by the health of the animal but the profits it generates!

    Thanks for sharing your opinion !

  27. v.t. says:

    Anne-Louise Koehl,

    No one is saying there aren’t problems with manufacturers, ethics, production etc.

    Because there may be certain problems in the industry does not make it true that raw meat diets for cats are better than commercial diets – there have been no studies to date that prove that assertion. As a matter of fact, feeding an ILL cat a raw meat diet may make matters worse since such a cat would be highly susceptible to pathogens, bacteria, etc. Again, no scientific studies in existence have shown raw meat diets are superior to any other, and in fact, are more prone to problems with the mentioned pathogens etc.

    Lastly, just because you aren’t hearing of any “ailments” from owners of cats fed raw meat diets does not mean they do not exist – it is more likely they are simply not being reported, tested for, overlooked, or that raw foodists are loathe to admit such problems occur.

  28. Susan says:

    And yet if you look at the FDA statistics for recalls for salmonella there are minimal recalls for raw food (15 630kg) by comparison to the recalls for processed kibble foods (49 40 827kgs) in a year. And according to the FDA statistics there were approximately 4500 pets (cats and dogs) killed in about three years to to salmonella poisoning from dry food and zero for the same in raw fed dogs.

    The FDA gather their statistics from the veterinary industry and not from the pet owners.

  29. skeptvet says:

    Comparing the number of recalls is not useful because the overwhelming majority of foods sold are not raw. There have to be more cases associated with conventional diets when the overwhelming majority of dogs eat these diets, not raw. What you are doing is like citing a statistic that Golden retrievers bite more people every year than wolves and then using this to argue that wolves are safer pets.

    Raw meat has been clearly shown to contain more pathogenic organisms than cooked meat. It is likely that the relative risk of infection is much higher for dogs eating raw meat compared to those eating cooked diets, though this will have to be proven by research not yet done.

  30. Kelly says:

    My reason for stopping the raw diet is how much did I know gets sick in my dogs teeth. I take very good care of her teeth however I don’t brush her after every feed. There are particles of rotting meat in my dogs mouth, she then licks me abd my grandsons and they just may not shears wash their hands. It’s a cleanliness issue. I use human food as my dog is small and it’s adorable but I do cook it. I get meat cuts on sale and cook them, cut them up and that’s get food. She never gets sick and almost 6 years old now.
    But kibble never enters my house. They put fiber in it and it keeps your dog pooping 6-7 times a day. My daughter’s dog literally poops that much. My dug who eats human food poops 1-2 times a day and it’s firm butt but not overly so. I knoe I’m feeding her clean good abd it’s important.
    Dogs are not wolves. And don’t forget wolves only live about 5 years much of that hungry and struggling to survive. It’s time to stop comparing domesticated dogs to wolves they gave retained very Few if any wolf traits, read the studies. They are almost a different species. Redesigned, bred to live with humans.

  31. Jill says:


    …do you think dogs don’t need fiber in their diets?

    Your anecdote about your daughter’s dog is easily contradicted by anecdotes about the opposite effect, for instance, this one: I have nine large dogs. I pick up my yard every day, I get about a half a plastic grocery bag full, just about one poop per dog, give or take.

    You’d think if there was some magic extra poop effect of kibble, a heavy user like myself would see it.

    And why do you think there is anything bad about a given number of BMs a day?

    How are you sure your dog gets proper nutrition?

    Kibble makers supported by veterinary nutritionists know more than we do.

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